Torsional rocking structural component

ABSTRACT

There is disclosed a torsional rocking structural component comprising: a movable plate; an elastic member for rockably supporting the movable plate, the elastic member having a rectangular parallelepiped shape, and a rectangular surface; a support for holding the elastic member; and a wiring passing through the elastic member, disposed in the vicinity of a surface of the elastic member and passing through a portion in which a stress generated during torsional deformation of the elastic member is small.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2000-208999, filed Jul.10, 2000, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a torsional rocking structuralcomponent for use in an optical scanner, angular acceleration sensor,and the like.

[0003] A torsional rocking structural component is a structure in whicha movable member is supported by a torsion spring structure. Examples ofa device using the torsional rocking structural component include anoptical scanner manufactured by a semiconductor process.

[0004] U.S. Pat. No. 5,606,447 titled “PLANAR TYPE MIRROR GALVANOMETERAND METHOD OF MANUFACTURE” issued to Asada et al. on Feb. 25, 1997discloses an electromagnetic driving actuator in which a torsionalrocking structural component is used. As shown in FIGS. 36 and 37, anactuator 1 is provided with a flat movable plate 5, two torsion bars 6a, 6 b for rockably supporting the movable plate 5, and a frame 2 forholding the torsion bars 6 a, 6 b, and these members are integrallyformed from a silicon substrate. The movable plate 5 includes: a flatcoil 7, disposed on an upper surface peripheral edge of the plate, forgenerating a magnetic field from a power supply; and a total reflectionmirror 8 disposed on an upper surface middle portion of the platesurrounded by the flat coil 7.

[0005] As shown in FIG. 37, upper and lower glass substrates 3 and 4 aredisposed on upper and lower surfaces of the frame 2, and permanentmagnets 10 a, 11 a and 10 b, 11 b for exerting a magnetic field onto theflat coil 7 are fixed at predetermined positions of the upper and lowerglass substrates 3 and 4.

[0006] Furthermore, as shown in FIG. 37, the frame 2 is provided with apair of electrode terminals 9 a, 9 b disposed on the upper surface ofthe frame, and the electrode terminals 9 a, 9 b are electricallyconnected to the flat coil 7 via coil wirings 12 a, 12 b extending alongthe respective upper surfaces of the torsion bars 6 a, 6 b. The flatcoil 7, electrode terminals 9 a, 9 b and coil wirings 12 a, 12 b aresimultaneously formed on the silicon substrate by an electroformingmethod.

[0007] As compared with a conventional actuator, the electromagneticactuator can be remarkably thinned.

[0008] In general, in the torsional rocking structural componentdisclosed in U.S. Pat. No. 5,606,447, a stress acts on the wiring due toa torsional movement. In this case, the wiring resistance changes, andin a worst case the wiring is sometimes disconnected by metal fatigue.

BRIEF SUMMARY OF THE INVENTION

[0009] The present invention has been developed to solve the problem,and an object thereof is to provide a torsional rocking structuralcomponent in which the influence of stress generated by repeatedtorsional movements is reduced.

[0010] Additional objects and advantages of the invention will be setforth in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0011] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate presently preferredembodiments of the invention, and together with the general descriptiongiven above and the detailed description of the preferred embodimentsgiven below, serve to explain the principles of the invention.

[0012]FIG. 1 is a perspective view of a model of a torsion springstructure designed to analyze the stress distribution generated in atorsion spring during torsional deformation.

[0013]FIG. 2 is a sectional view of the torsion spring taken along lineII-II of FIG. 1.

[0014]FIG. 3 shows a distribution of a shear stress τyz solved byapplying a torsion function derived from the Saint-Venant torsion theoryto the torsion spring having a rectangular sectional shape.

[0015]FIG. 4 shows a distribution of a shear stress τyx solved byapplying the torsion function derived from the Saint-Venant torsiontheory to the torsion spring having the rectangular sectional shape.

[0016]FIG. 5 shows a distribution of a normal stress σx obtained bysimulation in which a finite element method is used with respect to thetorsional deformation under the same conditions as that of analysis inFIGS. 3 and 4 with contour lines.

[0017]FIG. 6 shows a distribution of a normal stress σy obtained bysimulation in which the finite element method is used with respect tothe torsional deformation under the same conditions as that of analysisin FIGS. 3 and 4 with contour lines.

[0018]FIG. 7 shows a distribution of a shear stress τyx obtained bysimulation in which the finite element method is used with respect tothe torsional deformation under the same conditions as that of analysisin FIGS. 3 and 4 with contour lines.

[0019]FIG. 8 shows a distribution of the stress σx shown in FIG. 5 alonga path 1 passing through a middle portion of the torsion spring along alongitudinal axis.

[0020]FIG. 9 shows a distribution of the stress σy shown in FIG. 6 alongthe path 1 passing through the middle portion of the torsion springalong the longitudinal axis.

[0021]FIG. 10 shows a distribution of the stress τyx shown in FIG. 7along the path 1 passing through the middle portion of the torsionspring along the longitudinal axis.

[0022]FIG. 11 shows a distribution of the stress σx shown in FIG. 5along a path 2 passing in the vicinity of an end of the torsion spring.

[0023]FIG. 12 shows a distribution of the stress σy shown in FIG. 6along the path 2 passing in the vicinity of the end of the torsionspring.

[0024]FIG. 13 shows a distribution of the stress τyx shown in FIG. 7along the path 2 passing in the vicinity of the end of the torsionspring.

[0025]FIG. 14 shows a Von Mises stress distribution obtained bysimulation using the finite element method and generated in the vicinityof the upper surface of the torsion spring by the torsional deformationwith contour lines.

[0026]FIG. 15 shows a distribution of the Von Mises stress shown in FIG.14 along the path 1 passing through the middle portion of the torsionspring along the longitudinal axis.

[0027]FIG. 16 shows a distribution of the Von Mises stress shown in FIG.14 along the path 2 passing in the vicinity of the end of the torsionspring.

[0028]FIG. 17 is a perspective view of a torsional rocking structuralcomponent according to a first embodiment.

[0029]FIG. 18 is a sectional view of the torsional rocking structuralcomponent taken along line XVIII-XVIII of FIG. 17.

[0030]FIG. 19 is a sectional view taken along line XIX-XIX of thetorsional rocking structural component shown in FIG. 17.

[0031]FIG. 20 is a plan view of an enlarged portion of the torsionalrocking structural component of FIG. 17, showing a movable plate andelastic member.

[0032]FIG. 21 shows a first step of a process of manufacturing thetorsional rocking structural component according to the first embodimentwith a section taken along line XVIII′-XVIII of FIG. 17.

[0033]FIG. 22 shows a step subsequent to the step of FIG. 21 in theprocess of manufacturing the torsional rocking structural componentaccording to the first embodiment with the section taken along lineXVIII′-XVIII of FIG. 17.

[0034]FIG. 23 shows a step subsequent to the step of FIG. 22 in theprocess of manufacturing the torsional rocking structural componentaccording to the first embodiment with the section taken along lineXVIII′-XVIII of FIG. 17.

[0035]FIG. 24 shows a step subsequent to the step of FIG. 23 in theprocess of manufacturing the torsional rocking structural componentaccording to the first embodiment with the section taken along lineXVIII′-XVIII of FIG. 17.

[0036]FIG. 25 shows a step subsequent to the step of FIG. 24 in theprocess of manufacturing the torsional rocking structural componentaccording to the first embodiment with the section taken along lineXVIII′-XVIII of FIG. 17.

[0037]FIG. 26 shows a last step subsequent to the step of FIG. 25 in theprocess of manufacturing the torsional rocking structural componentaccording to the first embodiment with the section taken along lineXVIII′-XVIII of FIG. 17.

[0038]FIG. 27 is a partial plan view of the torsional rocking structuralcomponent according to a first modification of the torsional rockingstructural component of the first embodiment.

[0039]FIG. 28 is a partial plan view of the torsional rocking structuralcomponent according to a second modification of the torsional rockingstructural component of the first embodiment.

[0040]FIG. 29 is a partial plan view of the torsional rocking structuralcomponent according to a third modification of the torsional rockingstructural component of the first embodiment.

[0041]FIG. 30 is a perspective view of an electrostatic driving actuatorincluding the torsional rocking structural component according to afourth modification of the torsional rocking structural component of thefirst embodiment.

[0042]FIG. 31 is an enlarged partial plan view of the torsional rockingstructural component according to the fourth modification of thetorsional rocking structural component of the first embodiment shown inFIG. 30.

[0043]FIG. 32 is a partial plan view of the torsional rocking structuralcomponent according to a second embodiment of the present invention.

[0044]FIG. 33 is a partial plan view of the torsional rocking structuralcomponent according to a first modification of the torsional rockingstructural component of the second embodiment.

[0045]FIG. 34 is a partial plan view of the torsional rocking structuralcomponent according to a second modification of the torsional rockingstructural component of the second embodiment.

[0046]FIG. 35 is a partial plan view of the torsional rocking structuralcomponent according to a third embodiment of the present invention.

[0047]FIG. 36 is a plan view of an electromagnetic driving actuatorusing a conventional torsional rocking structural component.

[0048]FIG. 37 is a sectional view of the actuator taken along lineXXXVII-XXXVII of FIG. 36.

DETAILED DESCRIPTION OF THE INVENTION

[0049] Preferred embodiments of the present invention will be describedhereinafter with reference to the drawings.

[0050] Prior to the description of the embodiments, a stressdistribution generated in a torsion spring during torsional deformationwill first be described. Here, a model of a torsion spring structure 100shown in FIG. 1 is considered. As shown in FIG. 1, the torsion springstructure 100 comprises a torsion spring 102, a support 104 connected toone end of the torsion spring 102, and a movable plate 106 connected tothe other end of the torsion spring 102. The movable plate 106 issupported by the torsion spring 102 so as to be allowed to rock withrespect to the support 104 about a rocking axis, which extends throughthe torsion spring 102.

[0051] In the following consideration, the torsion spring 102 has asubstantially rectangular parallelepiped shape. That is, the torsionspring 102 has a uniform rectangular section along the rocking axis,excluding both ends, that is, vicinities of connection portions with thesupport 104 and movable plate 106. Moreover, the stress generated in thetorsion spring 102 by torsional deformation is within the elastic limitof a material of the torsion spring 102, and the material of the torsionspring 102 acts isotropically when deformed.

[0052] For the torsion spring 102 shown in FIG. 1, in a middle portionof the torsion spring 102, excluding the vicinities of the connectionportions with the support 104 and movable plate 106, an influence ofopposite-end restricted connection portions of the torsion spring may beignored, and a stress distribution can be derived from the Saint-Venanttorsion theory based on elasticity.

[0053] When respective stress components generated in the torsion spring102 are defined as shown in FIGS. 1 and 2, according to the Saint-Venanttorsion theory, among normal stresses σx, σy, σz and shear stresses τxy(=τyx), τxz (=τzx), τyz (=τzy), stress components σx, σy, σz, τxz arezero.

[0054] Furthermore, with respect to the shear stress τyz, FIG. 3 shows aresult obtained by applying a torsion function derived from theSaint-Venant torsion theory to a rectangular sectional shape of thetorsion spring and solving the function. This shear stress τyz issubstantially zero in the vicinity of the upper surface of FIG. 2. Onthe other hand, also for the shear stress τyx, similar to τyz, when thetorsion function is applied to the rectangular sectional shape andsolved, a stress distribution shown in FIG. 4 is obtained. The stressdistribution has a maximum value on a Z-axis of the rectangular sectionin the vicinity of the upper surface of FIG. 2, and is symmetrical withrespect to the Z-axis.

[0055] FIGS. 5 to 10 show simulation results in which a finite elementmethod is used with respect to the stress distribution generated bysimilar torsional deformation. FIGS. 5 to 7 show the stresses σx, σy,τyx generated in the vicinity of the upper surface of the torsion spring102 during the torsional deformation with contour lines. Moreover, FIGS.8 to 10 show a stress component distribution along a path 1 passingthrough a middle portion of the torsion spring 102 as for a longitudinalaxis in the stresses σx, σy, τyx of FIGS. 5 to 7.

[0056] Comparison of these results with the results obtained by theSaint-Venant torsion theory proves that the respective stress componentsof the middle portion of the torsion spring 102 follow the stressdistribution estimated from the torsion theory. Additionally, since astress component becomes negative on reversing the torsion angle, anabsolute value of the stress has to be evaluated. Moreover, by reversingthe torsion angle, the stress generated on the upper surface issimilarly generated also on the lower surface of the torsion spring 102.

[0057] On the other hand, the torsional deformation of the torsionspring 102 is restricted by the connection portions of the torsionspring 102 in the vicinity of the connection portions with the support104 and movable plate 106. Therefore, the deformation of the torsionspring 102 is not uniform along the rocking axis, and indicates adistribution different from that of the middle portion of the torsionspring 102. FIGS. 11 to 13 show the simulation results in which thefinite element method is used with respect to the stress distributiongenerated by the torsional deformation. FIGS. 11 to 13 show the stresscomponent distributions along a path 2 passing in the vicinity of theconnection portion in the stresses σx, σy, τyx of FIGS. 5 to 7.

[0058] Among the respective stress components, the normal stress ayalong the rocking axis indicates a maximum value in the vicinity of theupper surface close to the connection portion. Additionally, since thenormal stress σy is opposite on opposite sides of the rocking axis, thatis, a tensile stress and a compressive stress are generated, a linearelement having neither tensile nor compressive stress exists near therocking axis. As seen from FIG. 12, the stress is small in the vicinityof the linear element. The greater the distance from the linear elementis, the larger the stress becomes.

[0059] As described above, the stress τyx indicates the maximum value inthe middle portion of the torsion spring 102 and σy indicates themaximum value in the connection portion of the torsion spring 102 in therespective stress components. However, when breakage of a conductor(metal) is considered, it is important to specify a region having a highVon Mises stress value, which is broadly used as a yield condition of ametal or another isotropic material.

[0060] FIGS. 14 to 16 show the simulation results in which the finiteelement method is used with respect to the Von Mises stress distributiongenerated in the vicinity of the upper surface of the torsion spring bythe torsional deformation. Similar to FIGS. 5 to 10, the stressdistribution in the middle portion of the torsion spring 102 has amaximum value on the Z-axis of the rectangular section of FIG. 2, and issymmetrical with respect to the Z-axis. Moreover, the stressdistribution in the connection portion of the torsion spring 102 has amaximum value in the vicinity of opposite edges of the torsion spring102, and is symmetrical with respect to the Z-axis.

[0061] That is, the Von Mises stress distribution has a highest value inthe vicinity of the geometric center of the surface of the torsionspring 102. Moreover, the Von Mises stress distribution has a relativelyhigh value in the vicinity of geometric corners of the surface of thetorsion spring 102. Additionally, the high value of the Von Mises stressdistribution in the vicinity of the geometric center of the surface ofthe torsion spring 102 is mainly caused by a shear stress. On the otherhand, the high value of the Von Mises stress distribution in thevicinity of the geometric corners of the surface of the torsion spring102 is mainly caused by tensile stress.

[0062] The aforementioned stress distribution is an analysis result ofthe model of the torsion spring structure 100 shown in FIG. 1 in whichthe support 104 and movable plate 106 are connected to opposite ends ofthe torsion spring 102. Therefore, the distribution does not depend uponwhether the movable plate 106 has a center impeller structure or acantilever structure.

[0063] As described above, in the middle portion of the torsion spring102 along the rocking axis, the stress value is relatively high in thevicinity of the center as for a transverse axis that crosses at rightangles to the rocking axis. In opposite ends of the torsion spring 102along the rocking axis, the stress value is relatively high in thevicinity of the opposite edges as for the transverse axis crossing atright angles to the rocking axis. This can be generally described.

[0064] [First Embodiment]

[0065] A torsional rocking structural component of a first embodiment ofthe present invention will be described. In the first embodiment, thetorsional rocking structural component is applied to an electromagneticdriving actuator.

[0066] As shown in FIGS. 17 to 19, an actuator 200 is provided with atorsional rocking structural component 210, and a pair of permanentmagnets 202 a, 202 b. The torsional rocking structural component 210comprises a movable plate 212, a pair of elastic members 214 a, 214 bfor rockably supporting the movable plate 212, and a support 216 forretaining the elastic members 214 a, 214 b. The pair of elastic members214 a, 214 b symmetrically extend to opposite sides from the movableplate 212, and function as torsion bars. Therefore, the movable plate212 is supported so as to be allowed to rock with respect to the support216 about a rocking axis, which passes inside the elastic members 214 a,214 b.

[0067] Each of the elastic members 214 a, 214 b has a substantiallyrectangular parallelepiped shape, and a section of the member verticalto the rocking axis has a rectangular shape. In further detail, each ofthe elastic members 214 a, 214 b has one end in the vicinity of theconnection portion with the movable plate 212, the other end in thevicinity of the connection portion with the support 216, and a middleportion positioned between the ends. The middle portion has arectangular parallelepiped shape. Such a shape of the elastic member 214a or 214 b is generally selected because of ease of design andmanufacturing.

[0068] The movable plate 212 has a drive coil 222 drawn around aperipheral edge of the plate. The drive coil 222 has electrode pads 224a, 224 b on opposite ends. The support 216 is provided with a pair ofelectrode pads 226 a, 226 b for supplying an electric power to the drivecoil 222 from the outside. The torsional rocking structural component210 comprises a wiring 228 a passing through the elastic member 214 a,and the wiring 228 a electrically connects the electrode pad 224 a ofthe drive coil 222 to the electrode pad 226 a on the support.

[0069] Moreover, the torsional rocking structural component 210comprises a wiring 228 b passing through the elastic member 214 b. Oneend of the wiring 228 b is connected to the electrode pad 226 b on thesupport, and the other end thereof is connected to an electrode pad 230.Furthermore, the torsional rocking structural component 210 has a jumpwiring 232 extending across the drive coil 222 via an insulating layer,and the jump wiring 232 electrically connects the inner electrode pad224 b of the drive coil 222 to the electrode pad 230 of the wiring 228b.

[0070] The movable plate 212, elastic members 214 a, 214 b and support216 are monolithically formed from a single-crystal silicon substrate.Therefore, the single-crystal silicon is used as a main material in themovable plate 212, elastic members 214 a, 214 b and support 216. Thesingle-crystal silicon can be precisely processed, and is thereforepreferable for miniaturization of the torsional rocking structuralcomponent. Moreover, the single-crystal silicon is high in rigidity andlow in material internal damping, and therefore imparts superiorproperties to the elastic members 214 a, 214 b for resonance driving.Furthermore, the single-crystal silicon has high rigidity, and istherefore preferable for the material of the support 216 used as abonding portion for fixing the support to the outside.

[0071] The drive coil 222, electrode pads 224 a, 224 b, 226 a, 226 b,wirings 228 a, 228 b, and electrode pad 230 are formed of the same metalfilm, such as an aluminum film. The film is electrically insulated fromthe single-crystal silicon substrate as the main material of the movableplate 212, elastic members 214 a, 214 b and the support 216, forexample, by a silicon oxide film. Similarly, the jump wiring is alsoformed, for example, of an aluminum film, and electrically insulatedfrom the drive coil 222, for example, by a silicon oxide film.

[0072] Moreover, the metal film including the wirings 228 a, 228 b, andthe like is generally formed in the vicinity of the surface to aid easymanufacture. Therefore, the wirings 228 a, 228 b are positioned in thevicinity of the surfaces of the elastic members 214 a, 214 b,respectively.

[0073] The pair of permanent magnets 202 a, 202 b are disposed outsideopposite vibrating ends of the movable plate 212 and substantiallyparallel to the rocking axis. Magnetization directions of the permanentmagnets 202 a, 202 b are directed opposite to each other, and aresubstantially vertical to the surface of the movable plate 212 in astationary state. The permanent magnets 202 a, 202 b generate a magneticfield crossing at right angles to the rocking axis, so that a magneticfield component acts on drive coil 222 portions positioned on oppositeends of the movable plate 212 in a surface direction of the movableplate 212.

[0074] An operation of the actuator 200 will next be described. In FIG.17, when an alternating-current voltage is applied to two electrode pads226 a, 226 b on the support 216, an alternating current flows throughthe drive coil. 222. The current flowing in the portion of the drivecoil 222 in the vicinity of the permanent magnets 202 a, 202 b issubject to a Lorentz force by an interaction with the magnetic fieldgenerated by the permanent magnets 202 a, 202 b, and the movable plate212 is subjected to a couple in a plate thickness direction. Therefore,the movable plate 212 uses a center axis extending along a longitudinalaxis of two elastic members 214 a, 214 b as the rocking axis to rock,that is, to torsionally vibrate.

[0075] A moment for generating the torsional vibration is determined bya product of the Lorentz force acting on the drive coil 222 portions inthe vicinity of the permanent magnets 202 a, 202 b with a distancebetween the rocking axes passing through two elastic members 214 a, 214b and the drive coil 222 portions in the vicinity of the permanentmagnets 202 a, 202 b. The Lorentz force is determined by the propertiesof the permanent magnets 202 a, 202 b, the number of windings and wiringlength of the drive coil 222, current value, distance between thepermanent magnets 202 a, 202 b and the drive coil 222, and the like. Thedrive coil 222 is formed to turn around an outermost periphery of themovable plate 212, in order to increase the amount of force generatedand the moment.

[0076] When an alternating-current voltage having a frequency equal to aresonance frequency univocally determined by shapes and materials of themovable plate 212 and elastic members 214 a, 214 b is applied, themovable plate 212 vibrates with a maximum amplitude by the currentflowing through the drive coil 222. For example, when a reflectionmirror for reflecting a beam received from the outside is disposed onthe movable plate 212, the actuator 200 can be used as an opticalscanner for scanning the reflected beam.

[0077] In the first embodiment, as shown in FIG. 20, each of the wirings228 a, 228 b passes in the vicinity of one of the opposite edges of theelastic members 214 a, 214 b as for the transverse axis crossing atright angles to the rocking axis. That is, the wirings 228 a, 228 bextend, avoiding the vicinity of the geometric center of the surface ofthe elastic members 214 a, 214 b, in which a Von Mises stress ishighest. Therefore, the occurrence of disconnection of the wirings 228a, 228 b due to torsional movement of the elastic members 214 a, 214 bis reduced. Therefore, there is little fear that the wirings 228 a, 228b will be disconnected by torsional movement of the elastic members 214a, 214 b. As a result, the torsional rocking structural component 210having high reliability and durability can be obtained. Additionally, inan ordinary case, the rigidity of the wirings 228 a, 228 b can beignored as compared with the rigidity of the elastic members 214 a, 214b.

[0078] The torsional rocking structural component of the firstembodiment is prepared utilizing a semiconductor process. A method ofmanufacturing the torsional rocking structural component 210 of thefirst embodiment will be described hereinafter with reference to FIGS.21 to 26. FIGS. 21 to 26 show sections taken along line XVIII′-XVIII ofFIG. 17.

[0079] Step 1 (FIG. 21): A silicon on insulator (SOI) substrate 300 isprepared as a start wafer. The SOI substrate 300 is a structure obtainedby attaching a single-crystal silicon substrate 306, also called anactive layer substrate, to a silicon substrate 302, also called asupport substrate, via an insulating layer 304. The support substrate302 has a thickness, for example, of 200 to 500 μm, the insulating layer304 has a thickness, for example, of 1 μm, and the active layersubstrate 306 has a thickness, for example, of 100 μm. The SOI substrate300 is cleaned, a thermal oxide film 310 is formed on a front surface ofthe substrate, and a thermal oxide film 308 is formed on a back surfaceof the substrate.

[0080] Step 2 (FIG. 22): The thermal oxide film 308 formed on the backsurface of the SOI substrate 300 is used as a mask material forseparating the movable plate 212 and support 216 from the back surface.Moreover, the thermal oxide film 310 formed on the front surface of theSOI substrate 300 is used as a mask material for forming the movableplate 212, elastic members 214 a, 214 b and support 216 from the frontsurface. Therefore, portions from which silicon is later to be removedare removed beforehand from the thermal oxide films 308 and 310 byetching.

[0081] Step 3 (FIG. 23): An aluminum thin film 312 is formed on thefront-surface thermal oxide film 310 by sputtering, and etched, so thatthe drive coil 222, electrode pad 224 b, wiring 228 b, electrode pad 226b, and the like are formed.

[0082] Step 4 (FIG. 24): Subsequently, for example, the plasma oxidefilm 312 for forming an interlayer insulating film is formed. Only aportion with the front-surface thermal oxide film 310 etched therefromand with silicon exposed thereto, a portion for forming an interlayercontact, the electrode pad 226 b, and other upper portions are removedby etching. Furthermore, a second aluminum thin film 314 is formed onthe plasma oxide film 312 by sputtering, and etched, so that the jumpwiring 232 for connecting the inner electrode pad 224 b of the drivecoil 222 to the outside of the coil is formed. Additionally, in order toprotect the jump wiring 232 from rusting, the second plasma oxide film314 is formed only on the upper portion of the jump wiring 232.

[0083] Step 5: (FIG. 25): The active layer substrate 306 of the SOIsubstrate 300 is etched from the front surface in the form of themovable plate 212, elastic members 214 a, 214 b and support 216 by dryetching. In this case, a reactive ion etching (RIE) is performedutilizing an inductively-coupled plasma (ICP), and thereby an etchedside surface is processed substantially vertically to the substratesurface. The etching reaches the insulating layer 304 of the SOIsubstrate 300 and then stops. Subsequently, in order to form the movableplate 212 and support 216 on the back surface, an alkaline solution isused to perform an anisotropic etching on the silicon substrate 302 fromthe back surface of the SOI substrate 300.

[0084] Step 6 (FIG. 26): After the etching of the silicon substrate 302,the insulating layer 304 exposed on the back surface of the elasticmembers 214 a, 214 b and between the movable plate 212 and the support216 is removed by dry etching, and the torsional rocking structuralcomponent 210 is completed. When the torsional rocking structuralcomponent 210 is used, for example, as an optical scanner, it ispreferable to sputter gold or aluminum on the back surface of themovable plate 212 and form a reflection surface having a highreflectance if necessary.

[0085] As described above, since the torsional rocking structuralcomponent 210 of the first embodiment is integrally formed utilizing thesemiconductor manufacturing technique, a subsequent assembly operationis unnecessary, and a large amount of microfine and inexpensivetorsional rocking structural component can be produced. Additionally,the dimensional precision is very high, and therefore variations in theproperties of the material are very low.

[0086] The respective constitutions of the first embodiment are notlimited to the aforementioned constitutions, and can be variouslymodified or changed.

[0087] For example, the drive coil 222 is formed by aluminum sputteringfilm formation and etching, but may be formed by plating. Particularly,when a large deflection angle is necessary, the number of windings ofthe drive coil 222 needs to be increased. However, if only the number ofwindings is increased without increasing the sectional area of the coil,the coil resistance increases. This results in an increase of the powervoltage or power consumption. A coil having a thickness greater than thethickness of the coil prepared by sputtering is formed by plating, theaspect ratio is thereby enhanced, and predetermined specifications canbe satisfied.

[0088] Moreover, the driving method is not limited to a reciprocatingdriving method by the alternating current having the frequency equal tothe resonance frequency. For example, the device may be staticallypositioned by driving it, for example, by a variable frequency or adirect current.

[0089] Modifications of the first embodiment will be describedhereinafter with reference to the drawings. In the followingdescription, members equivalent to the aforementioned members aredenoted with the same reference numerals, and a detailed descriptionthereof is omitted.

[0090] In the torsional rocking structural component of a firstmodification, as shown in FIG. 27, both the wirings 228 a and 228 b passthrough the elastic member 214 a. In further detail, the wirings 228 a,228 b pass in the vicinity of the opposite edges of the elastic member214 a. In other words, the wirings 228 a, 228 b extend, avoiding thevicinity of the geometric center of the surface of the elastic member214 a in which the Von Mises stress is highest. Therefore, there islittle fear that the wirings 228 a, 228 b are disconnected by torsionalmovement of the elastic member 214 a.

[0091] Moreover, the wirings 228 a, 228 b are arranged symmetricallywith respect to the rocking axis. Therefore, the elastic member 214 ahas torsion properties with satisfactory symmetry with respect to atorsion direction.

[0092] The opposite-side elastic member 214 b may be provided with dummywirings 234 a, 234 b, in order to enhance the symmetry of the torsionproperties of the left and right elastic members 214 a, 214 b. The dummywirings 234 a, 234 b are formed of the same material as that of thewirings 228 a, 228 b. Similarly as the wirings 228 a, 228 b, the dummywiring may pass in the vicinity of the opposite edges of the elasticmember 214 b.

[0093] Moreover, in the torsional rocking structural component of thefirst modification, since both of two wirings 228 a, 228 b pass throughthe elastic member 214 a, two electrode pads 226 a, 226 b are disposedin the vicinity. This arrangement provides an advantage that anoperation for connecting the wiring to the outside can be easilyperformed.

[0094] As shown in FIG. 28, the torsional rocking structural componentof a second modification includes the movable plate 212, one elasticmember 214 for rockably supporting the movable plate 212, and thesupport 216 for holding the elastic member 214. That is, the movableplate 212 is supported by a cantilever structure so as to be allowed torock.

[0095] The wirings 228 a, 228 b pass in the vicinity of the oppositeedges of the elastic member 214. That is, the wirings 228 a, 228 bextend, avoiding the vicinity of the geometric center of the surface ofthe elastic member 214 in which the Von Mises stress is highest.Therefore, there is little fear that the wirings 228 a, 228 b aredisconnected by the torsional movement of the elastic member 214.

[0096] In the torsional rocking structural component of a thirdmodification, as shown in FIG. 29, the wirings 228 a, 228 b pass in thevicinity of one of the opposite edges of the elastic members 214 a, 214b in the middle portions of the elastic members 214 a, 214 b. In theends of the elastic members 214 a, 214 b, that is, in the vicinity ofthe connection portions with the movable plate 212 and support 216, thewirings 228 a, 228 b pass in the vicinity of the center of the elasticmembers 214 a, 214 b as for the transverse axis crossing at right anglesto the rocking axis.

[0097] As described above, the Von Mises stress distribution has ahighest value in the vicinity of the geometric center of the surface ofthe torsion spring 102, and has a relatively high value in the vicinityof the geometric corners of the surface of the torsion spring 102.Therefore, in other words, the wirings 228 a, 228 b extend, avoiding thevicinity of the geometric center of the surface of the elastic members214 a, 214 b in which the Von Mises stress is highest, and avoiding thevicinity of the geometric corners of the surface of the elastic members214 a, 214 b in which the Von Mises stress is relatively high.Therefore, in the third modification, there is little fear that thewirings 228 a, 228 b are disconnected by the torsional movement of theelastic member 214 a.

[0098] According to a fourth modification, there is a torsional rockingstructural component applied to an electrostatic driving actuator. Inthe torsional rocking structural component of the fourth modification,as shown in FIGS. 30 and 31, the movable plate 212 is provided with apair of movable electrodes 242 a, 242 b. The movable electrodes 242 a,242 b are symmetrically arranged on the opposite sides of the rockingaxis, respectively. The movable electrode 242 a is electricallyconnected to the electrode pad 226 a positioned on the support 216 viathe wiring 228 a passing through the elastic member 214 a. Similarly,the movable electrode 242 b is electrically connected to the electrodepad 226 b positioned on the support 216 via the wiring 228 b passingthrough the elastic member 214 b.

[0099] The actuator is provided with a fixed electrode 244 fixed to afixing member (not shown). The fixed electrode 244 is disposed oppositeto the movable electrodes 242 a, 242 b disposed on the movable plate212. The fixed electrode 244 is connected to the electrode pads 226 a,226 b via a power supply 246 and switch 248. The switch 248 is changedover to selectively apply a potential difference between one of themovable electrodes 242 a, 242 b and the fixed electrode 244. As aresult, an electrostatic attraction force is generated between one ofthe movable electrodes 242 a, 242 b and the fixed electrode 244 becauseof the potential difference applied therebetween. Thereby, the movableplate 212 follows the electrostatic attraction force and is inclined ina corresponding direction. When the switch 248 is alternately operated,the movable plate 212 is vibrated about the rocking axis passing throughthe elastic members 214 a, 214 b.

[0100] As shown in FIG. 31, the wirings 228 a, 228 b pass in thevicinity of one of the opposite edges of the elastic members 214 a, 214b. That is, the wirings 228 a, 228 b extend, avoiding the vicinity ofthe geometric center of the surface of the elastic members 214 a, 214 bin which the Von Mises stress is highest. Therefore, there is littlefear that the wirings 228 a, 228 b are disconnected by the torsionalmovement of the elastic member 214 a.

[0101] The actuator including the torsional rocking structural componentof the present modification may be driven by a method other than themethod of operating the switch 248. For example, two electrode pads 226a, 226 b may be connected to separate variable power supplies. In thiscase, the actuator is driven by applying predetermined voltages from therespective variable power supplies.

[0102] Moreover, the modifications shown in FIGS. 27 to 29 may beapplied to the torsional rocking structural component of the presentmodification applied to the electrostatic driving actuator.

[0103] In any one of the aforementioned embodiments and modifications,the torsional rocking structural component with 1 degree of freedom hasbeen illustrated, but the present invention may be applied to thetorsional rocking structural component with 2 degrees of freedom such asa gimbal structure.

[0104] [Second Embodiment]

[0105] The torsional rocking structural component of a second embodimentof the present invention will be described. The torsional rockingstructural component of the second embodiment is constituted by adding avibration detection coil to the torsional rocking structural componentof the first embodiment. In the following description, membersequivalent to the members described above in the first embodiment aredenoted with the same reference numerals, and a detailed descriptionthereof is omitted.

[0106] As shown in FIG. 32, the torsional rocking structural componentof the second embodiment comprises the movable plate 212, the pair ofelastic members 214 a, 214 b for rockably supporting the movable plate212, the elastic members allowing the movable plate 212 to rock about arocking axis extending inside of thereof, and the support 216 forholding the elastic members 214 a, 214 b. The movable plate 212 isprovided with the drive coil 222 drawn around the peripheral edge of theplate, and a vibration detection coil 252 drawn inside the drive coil222.

[0107] The torsional rocking structural component 210 also comprises thewirings 228 a, 228 b passing through the elastic member 214 a. One endof the wiring 228 a is connected to the electrode pad 226 a on thesupport, and the other end thereof is connected to the electrode pad 224a of the drive coil 222. One end of the wiring 228 b is connected to theelectrode pad 226 b on the support, and the other end thereof isconnected to the electrode pad 230. The electrode pad 230 is connectedto the inner electrode pad 224 b of the drive coil 222 via the jumpwiring 232 extending across the drive coil 222 via the insulating layer.

[0108] The torsional rocking structural component 210 further compriseswirings 258 a, 258 b passing through the elastic member 214 b. One endof the wiring 258 a or 258 b is connected to an electrode pad 256 a or256 b on the support 216, and the other end thereof is connected to anelectrode pad 260 a or 260 b. The electrode pads 260 a, 260 b areconnected to electrode pads 254 a, 254 b of the vibration detection coil252 via jump wirings 262 a, 262 b extending across the drive coil 222and vibration detection coil 252 via the insulating layer.

[0109] The wirings 228 a, 228 b pass in the vicinity of the oppositeedges of the elastic member 214 a. That is, the wirings 228 a, 228 bextend, avoiding the vicinity of the geometric center of the surface ofthe elastic members 214 a in which the Von Mises stress is highest.Therefore, there is little fear that the wirings 228 a, 228 b aredisconnected by the torsional movement of the elastic member 214 a.Moreover, the wirings 228 a, 228 b are arranged symmetrically withrespect to the rocking axis. Therefore, the elastic member 214 a hastorsion properties having satisfactory symmetry with respect to thetorsion direction.

[0110] Similarly, the wirings 258 a, 258 b pass in the vicinity of theopposite edges of the elastic member 214 b. That is, the wirings 258 a,258 b extend, avoiding the vicinity of the geometric center of thesurface of the elastic members 214 b in which the Von Mises stress ishighest. Therefore, there is little fear that the wirings 258 a, 258 bare disconnected by the torsional movement of the elastic member 214 b.Moreover, the wirings 258 a, 258 b are arranged symmetrically withrespect to the rocking axis. Therefore, the elastic member 214 b hastorsional properties having a satisfactory symmetry with respect to thetorsion direction.

[0111] Furthermore, the elastic members 214 a, 214 b have the wirings228 a, 228 b, 258 a, 258 b. The wirings 228 a, 228 b, 258 a, 258 b arepreferably formed of the same material, and are symmetrically disposed.Therefore, the elastic members 214 a, 214 b have substantially the sametorsional properties.

[0112] The torsional rocking structural component of the secondembodiment is manufactured by a manufacturing method similar to that ofthe torsional rocking structural component of the first embodiment. Thesecond embodiment is the same as the first embodiment, except that thevibration detection coil 252 is simultaneously formed during formationof the drive coil 222, and a detailed description thereof is omitted.

[0113] Similarly as the torsional rocking structural component of thefirst embodiment, the torsional rocking structural component of thesecond embodiment is applied to the electromagnetic driving actuator. Adriving method of the actuator is the same as that of the actuatorincluding the torsional rocking structural component of the firstembodiment, and a detailed description thereof is omitted.

[0114] The actuator including the torsional rocking structural componentof the second embodiment can monitor a vibration state of the movableplate 212. With the vibration of the movable plate 212, the vibrationdetection coil 252 moves within the magnetic field formed by thepermanent magnet. Therefore, electromagnetic induction generates anelectromotive force in the vibration detection coil 252. A polarity ofthe electromotive force is determined by a movement direction of thevibration detection coil 252, and a size of the force is determined by amagnetic flux density, coil winding number, coil movement speed, coillength in the magnetic field, and the like.

[0115] As a result, a signal proportional to the vibration speed of themovable plate 212 is outputted from the vibration detection coil 252.Therefore, the vibration state of the movable plate 212 can be monitoredbased on the signal. Moreover, the vibration of the movable plate 212can also be controlled based on the signal. Concretely, based on theoutput signal of the vibration detection coil 252, changes of aresonance frequency and deflection angle caused by an environmentalchange, and the like can be controlled and automatically corrected.

[0116] Similarly as the first embodiment, when the reflection mirror forreflecting the beam incident from the outside is disposed on the movableplate 212, the actuator can be used as the optical scanner for scanningthe reflected beam. Moreover, the properties that enable the actuator todetect the deflection angle are utilized, and the actuator can also beused as a sensor for detecting an angular speed and acceleration.

[0117] As described above, in the torsional rocking structural componentof the second embodiment, the wirings 228 a, 228 b passing through theelastic member 214 a and wirings 258 a, 258 b passing through theelastic member 214 b extend, avoiding the vicinity of the geometriccenter of the surface of the elastic members 214 a, 214 b in which theVon Mises stress is highest. Therefore, there is little fear that thewirings 228 a, 228 b, 258 a, 258 b are disconnected by the torsionalmovement of the elastic members 214 a, 214 b. Therefore, the torsionalrocking structural component having high reliability and durability canbe obtained.

[0118] Moreover, since the torsional rocking structural component of thesecond embodiment is integrally formed utilizing the semiconductormanufacturing technique, the subsequent assembly operation isunnecessary, and a large amount of the microfine and inexpensivetorsional rocking structural component can be produced. Additionally,the dimensional precision is very high, and the properties dispersion istherefore remarkably little.

[0119] The respective constitutions of the second embodiment are notlimited to the aforementioned constitutions, and can variously bemodified or changed.

[0120] For example, the drive coil 222 is formed by aluminum sputteringfilm formation and etching processing similarly as in the firstembodiment, but may be formed by plating. Particularly, when the aspectratio of the drive coil 222 is enhanced by plating, the coil resistanceis prevented from increasing, and an increase of the power voltage andpower consumption is suppressed. In addition to these advantages, anoccupied width of the drive coil 222 can advantageously be reduced.Therefore, the drive coil 222 can be disposed further in the vicinity ofthe peripheral edge of the movable plate 212, and the sensitivity of thevibration detection coil 252 can be enhanced. Alternatively, the drivecoil 222 and vibration detection coil 252 may be formed in separatesuperposed layers via the insulating layer. Particularly, to enhance thesensitivity, the vibration detection coil 252 is superposed onto thedrive coil 222 and formed in the vicinity of the peripheral edge of themovable plate 212.

[0121] Moreover, the drive coil 222 and vibration detection coil 252 areseparately disposed, but one coil may serve both as the drive coil 222and the vibration detection coil 252. For example, this can be realizedby a changeover switch disposed to change between a case in which thecoil is connected to the power source to serve as the drive coil and acase in which the coil is connected to a detection circuit to serve asthe vibration detection coil. In this manner, the driving and thevibration detection are alternated with time. In this case, theconstitution of the torsional rocking structural component is the sameas that of the torsional rocking structural component of the firstembodiment.

[0122] Moreover, the driving method is not limited to the reciprocatingdriving method by using an alternating current having a frequency equalto the resonance frequency. For example, the device may be staticallypositioned by driving it, for example, by a variable frequency or adirect current.

[0123] Modifications of the second embodiment will be describedhereinafter with reference to the drawings. In the followingdescription, the members equivalent to the aforementioned members aredenoted with the same reference numerals, and a detailed descriptionthereof is omitted.

[0124] In the torsional rocking structural component of a firstmodification, as shown in FIG. 33, the wirings 228 a, 228 b, 258 a, 258b pass through the elastic member 214 a. In further detail, the wirings228 a, 228 b pass in the vicinity of one of the opposite edges of theelastic member 214 a, and the wirings 258 a, 258 b pass in the vicinityof the other edge of the elastic member 214 a. In other words, thewirings 228 a, 228 b, 258 a, 258 b extend, avoiding the vicinity of thegeometric center of the surface of the elastic member 214 a in which theVon Mises stress is highest. Therefore, there is little fear that thewirings 228 a, 228 b, 258 a, 258 b are disconnected by the torsionalmovement of the elastic member 214 a. Additionally, the outer wiring 228a is different from the inner wiring 228 b in the stress acting on thewiring. Similarly, the inner wiring 258 a is different from the outerwiring 258 b in the stress acting on the wiring. Therefore, attentionmust be paid in order to maintain reliability.

[0125] Moreover, the wirings 228 a, 228 b, and the wirings 258 a, 258 bare arranged symmetrically with respect to the rocking axis. Therefore,the elastic member 214 a has torsion properties having a satisfactorysymmetry with respect to the torsion direction.

[0126] The opposite-side elastic member 214 b may be provided with dummywirings 234 a, 234 b, 264 a, 264 b in order to enhance the symmetry ofthe torsion properties of the left and right elastic members 214 a, 214b. The dummy wirings 234 a, 234 b, 264 a, 264 b are formed of the samematerial as that of the wirings 228 a, 228 b, 258 a, 258 b. Similarly asthe wirings 228 a, 228 b, 258 a, 258 b, the dummy wirings 234 a, 234 b,264 a, 264 b may pass in the vicinity of the opposite edges of theelastic member 214 b.

[0127] Moreover, for the torsional rocking structural component of thefirst modification, since all of the four wirings 228 a, 228 b, 258 a,258 b pass through the elastic member 214 a, four electrode pads 226 a,226 b, 256 a, 256 b are positioned in the vicinity. Therefore, theoperation for connecting the wiring to the outside can be advantageouslyand easily performed.

[0128] As another modification of the torsional rocking structuralcomponent of the second embodiment, the elastic member 214 b may beomitted, so that the movable plate 212 is supported only by the elasticmember 214 a in a cantilever manner.

[0129] In the torsional rocking structural component of a secondmodification, as shown in FIG. 34, the wirings 228 a, 228 b pass in thevicinity of the opposite edges of the elastic member 214 a in thevicinity of the middle portion of the elastic member 214 a along therocking axis, and pass in the vicinity of the center of the elasticmember 214 a as for the transverse axis in the vicinity of theconnection portions with the movable plate 212 and support 216.Similarly, the wirings 258 a, 258 b pass in the vicinity of the oppositeedges of the elastic member 214 b in the middle portion of the elasticmember 214 b, and pass in the vicinity of the center of the elasticmember 214 b as for the transverse axis in the vicinity of theconnection portions with the movable plate 212 and support 216.

[0130] As described above, the Von Mises stress distribution has ahighest value in the vicinity of the geometric center of the surface ofthe torsion spring 102, and has a relatively high value in the vicinityof the geometric corners of the surface of the torsion spring 102.Therefore, in other words, the wirings 228 a, 228 b, 258 a, 258 bextend, avoiding the vicinity of the geometric center of the surface ofthe elastic members 214 a, 214 b in which the Von Mises stress ishighest because of the shear stress, and avoiding the vicinity of thegeometric corners of the surface of the elastic members 214 a, 214 b inwhich the Von Mises stress is relatively high because of the tensilestress. Therefore, in the second modification, there is little fear thatthe wirings 228 a, 228 b, 258 a, 258 b are disconnected by the torsionalmovement of the elastic members 214 a, 214 b.

[0131] In any one of the aforementioned embodiments and modifications,the torsional rocking structural component with 1 degree of freedom hasbeen illustrated, but the present invention may be applied to thetorsional rocking structural component with 2 degrees of freedom such asthe gimbal structure.

[0132] [Third Embodiment]

[0133] The torsional rocking structural component of a third embodimentof the present invention will be described. The torsional rockingstructural component of the third embodiment is constituted by disposinga strain detection element for detecting the vibration of the movableplate 212 on the torsional rocking structural component of the firstembodiment, instead of the vibration detection coil of the secondembodiment. In the following description, the members equivalent to themembers described above in the first embodiment are denoted with thesame reference numerals, and a detailed description thereof is omitted.

[0134] As shown in FIG. 35, the torsional rocking structural componentof the third embodiment comprises the movable plate 212, the pair ofelastic members 214 a, 214 b for rockably supporting the movable plate212, the elastic members allowing the movable plate 212 to rock about arocking axis extending inside of thereof, and the support 216 forholding the elastic members 214 a, 214 b. The movable plate 212 isprovided with the drive coil 222 drawn around the peripheral edge of theplate.

[0135] The torsional rocking structural component 210 also comprises thewirings 228 a, 228 b passing through the elastic member 214 a. One endof the wiring 228 a is connected to the electrode pad 226 a on thesupport, and the other end thereof is connected to the electrode pad 224a of the drive coil 222. One end of the wiring 228 b is connected to theelectrode pad 226 b on the support, and the other end thereof isconnected to the electrode pad 230. The electrode pad 230 is connectedto the inner electrode pad 224 b of the drive coil 222 via the jumpwiring 232 extending across the drive coil 222 via the insulating layer.

[0136] The torsional rocking structural component 210 further comprisesa pair of strain detection elements 272 a, 272 b. The strain detectionelements 272 a, 272 b are disposed on the elastic member 214 b. Moreparticularly, the elements are disposed in the vicinity of theconnection portion with the movable plate 212 and in the vicinity of theopposite edges of the elastic member 214 b. That is, the straindetection elements 272 a, 272 b are disposed in the vicinity of thegeometric corners of the surface of the elastic member 214 b in whichthe Von Mises stress is relatively high because of the tensile stress.

[0137] The strain detection elements 272 a, 272 b are electricallyconnected to electrode pads 276 a, 276 b disposed on the support 216 viawirings 274 a, 274 b passing through the elastic member 214 b.

[0138] The wirings 228 a, 228 b pass in the vicinity of the oppositeedges of the elastic member 214 a in the vicinity of the middle portionof the elastic member 214 a along the rocking axis, and pass in thevicinity of the center of the elastic member 214 a as for the transverseaxis in the vicinity of the connection portions with the movable plate212 and support 216. Similarly, the wirings 274 a, 274 b pass in thevicinity of the opposite edges of the elastic member 214 b in thevicinity of the middle portion of the elastic member 214 b, and pass inthe vicinity of the center of the elastic member 214 b as for thetransverse axis in the vicinity of the connection portions with themovable plate 212 and support 216.

[0139] As described above, the Von Mises stress distribution has ahighest value in the vicinity of the geometric center of the surface ofthe torsion spring 102, and has a relatively high value in the vicinityof the geometric corners of the surface of the torsion spring 102.Therefore, in other words, the wirings 228 a, 228 b, 274 a, 274 bextend, avoiding the vicinity of the geometric center of the surface ofthe elastic members 214 a, 214 b in which the Von Mises stress ishighest because of the shear stress, and avoiding the vicinity of thegeometric corners of the surface of the elastic members 214 a, 214 b inwhich the Von Mises stress is relatively high because of the tensilestress. Therefore, in the modification, there is little fear that thewirings 228 a, 228 b, 274 a, 274 b are disconnected by the torsionalmovement of the elastic members 214 a, 214 b.

[0140] Moreover, the wirings 228 a, 228 b, and wirings 274 a, 274 b arearranged symmetrically with respect to the elastic members 214 a, 214 b,respectively, and with respect to the rocking axis. Therefore, theelastic members 214 a and 214 b have torsion properties having thesatisfactory symmetry with respect to the torsion direction.

[0141] The torsional rocking structural component of the thirdembodiment is manufactured by the manufacturing method similar to thatof the torsional rocking structural component of the first embodiment.The third embodiment is the same as the first embodiment, except thatthe strain detection elements 272 a, 272 b are disposed and the wirings274 a, 274 b and electrode pads 276 a, 276 b connected to the elementsare formed simultaneously with the drive coil 222, and a detaileddescription of the third embodiment is omitted.

[0142] Similarly as the torsional rocking structural component of thefirst embodiment, the torsional rocking structural component of thethird embodiment is applied to the electromagnetic driving actuator. Thedriving method of the actuator is the same as that of the actuatorincluding the torsional rocking structural component of the firstembodiment, and a detailed description thereof is omitted.

[0143] The actuator including the torsional rocking structural componentof the third embodiment can monitor the vibration state of the movableplate 212 by the strain detection elements 272 a, 272 b. With thevibration of the movable plate 212, a strain is generated in the elasticmembers 214 a, 214 b. The strain detection elements 272 a, 272 b outputa signal in accordance with the strain generated in the elastic member214 b. The polarity of the output signal of the strain detectionelements 272 a, 272 b is determined by the torsion direction of movableplate 212, and a signal size is determined by the torsion angle of themovable plate 212.

[0144] In this manner, the output signals of the strain detectionelements 272 a, 272 b reflect the vibration state of the movable plate212. Therefore, the vibration state of the movable plate 212 can bemonitored based on the signal. Moreover, the vibration of the movableplate 212 can also be controlled based on the signal. Concretely, theresonance frequency change and deflection angle change caused by theenvironmental change can be controlled and automatically corrected basedon the output signals of the strain detection elements 272 a, 272 b.

[0145] In the conventional apparatus using the strain detection element,an optimum position in which the strain detection element is disposed isnot taught. In the third embodiment, the optimum position in which thestrain detection element is disposed is taught. That is, the straindetection elements 272 a, 272 b may be disposed in the vicinity of theopposite edges of the elastic member 214 b in the vicinity of theconnection portion with the movable plate 212. In other words, theelement may be disposed in the vicinity of the geometric corners of thesurface of the elastic member 214 b. This is a position in which the VonMises stress is relatively high because of the tensile stress. In thetorsional rocking structural component of the third embodiment, sincethe strain detection elements 272 a, 272 b are disposed in the positionhaving the high Von Mises stress, the vibration state of the movableplate 212 can be detected with a satisfactory sensitivity.

[0146] Similarly as the first embodiment, when the reflection mirror forreflecting the beam incident from the outside is disposed on the movableplate 212, the actuator can be used as the optical scanner for scanningthe reflected beam. Moreover, the properties that enable the actuator todetect the deflection angle are utilized, and the actuator can also beused as a sensor for detecting angular speed and acceleration.

[0147] Moreover, since the torsional rocking structural component of thethird embodiment is integrally formed utilizing the semiconductormanufacturing technique, the subsequent assembly operation isunnecessary, and a large amount of the microfine and inexpensivetorsional rocking structural component can be produced. Additionally,the dimensional precision is very high, and variations in the propertiesof the material are very low.

[0148] The respective constitutions of the third embodiment are notlimited to the aforementioned constitutions, and can be variouslymodified or changed.

[0149] For example, the drive coil 222 is formed by aluminum sputteringfilm formation and etching similarly as the first embodiment, but may beformed by plating. Particularly, when the aspect ratio of the drive coil222 is enhanced by plating, the coil resistance is prevented fromincreasing, and an increase of the power voltage and power consumptionis suppressed. In addition to these advantages, the occupied width ofthe drive coil 222 can be advantageously reduced. Therefore, the drivecoil 222 can be disposed further in the vicinity of the peripheral edgeof the movable plate 212, and a larger driving force can be obtained.

[0150] Moreover, the driving method is not limited to the reciprocatingdriving method by the alternating current having a frequency equal tothe resonance frequency. For example, the constitution may statically bepositioned by driving the constitution, for example, by a variablefrequency or a direct current.

[0151] The strain detection elements 272 a, 272 b and wirings 274 a, 274b may be disposed in the elastic member 214 a. That is, the straindetection elements 272 a, 272 b are disposed in the vicinity of theopposite edges of the elastic member 214 a in the vicinity of theconnection portion with the movable plate 212, that is, in the vicinityof the geometric corners of the surface of the elastic member 214 b inwhich the Von Mises stress is relatively high because of the tensilestress. The wirings 274 a, 274 b connected to the strain detectionelements 272 a, 272 b may pass through the elastic member 214 a outsidethe wirings 228 a, 228 b, and may be electrically connected to theelectrode pads 276 a, 276 b disposed on the support 216 in the vicinityof the electrode pads 226 a, 226 b.

[0152] In this case, the wirings 228 a, 272 a and wirings 228 b, 272 bextend, avoiding the vicinity of the geometric center of the surface ofthe elastic member 214 a in which the Von Mises stress is highest.Therefore, there is little fear that the wirings 228 a, 228 b, 272 a,272 b are disconnected by the torsional movement of the elastic member214 a. Additionally, the outer wirings 274 a, 274 b are different fromthe inner wirings 228 a, 228 b in the stress acting on the wiring.Therefore, attention is necessary for securing the reliability.

[0153] Moreover, since the wirings 228 a, 272 a and wirings 228 b, 272 bare arranged symmetrically with respect to the rocking axis, the elasticmember 214 a has torsion properties with satisfactory symmetry withrespect to the torsion direction. Furthermore, since four electrode pads226 a, 226 b, 272 a, 272 b are positioned in the vicinity, the operationfor connecting the wiring to the outside can easily be performed.

[0154] Furthermore, in order to enhance the symmetry of the torsionproperties of the left and right elastic members 214 a, 214 b, for theopposite-side elastic member 214 b, four corresponding dummy wirings maypreferably be disposed on the wirings 228 a, 228 b, 272 a, 272 b.

[0155] As a further modification, the elastic member 214 b may beomitted, and the movable plate 212 may be supported only by the elasticmember 214 a in a cantilever manner.

[0156] In any one of the aforementioned embodiments and modifications,the torsional rocking structural component with 1 degree of freedom hasbeen illustrated, but the third embodiment may be applied to thetorsional rocking structural component with 2 degrees of freedom such asthe gimbal structure. Moreover, the present invention may be applied tothe torsional rocking structural component for use in the electrostaticdriving actuator.

[0157] Some embodiments have been concretely described above withreference to the drawings, but the present invention is not limited tothe aforementioned embodiments, and includes all embodiments within thescope of the present invention.

[0158] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A torsional rocking structural componentcomprising: a movable plate; an elastic member for rockably supportingthe movable plate, the elastic member having a rectangularparallelepiped shape, and a rectangular surface; a support for holdingthe elastic member; and a wiring passing through the elastic member,disposed in the vicinity of a surface of the elastic member and passingthrough a portion in which a stress generated during torsionaldeformation of the elastic member is small.
 2. The torsional rockingstructural component according to claim 1 wherein the wiring extends,avoiding the vicinity of a geometric center of the surface of theelastic member.
 3. The torsional rocking structural component accordingto claim 2 wherein the wiring extends, avoiding the vicinity ofgeometric corners of the surface of the elastic member.
 4. A torsionalrocking structural component comprising: a movable plate; an elasticmember for rockably supporting the movable plate, the elastic memberhaving a rectangular parallelepiped shape, and a rectangular surface; asupport for holding the elastic member; and two wirings passing throughthe elastic member, disposed in the vicinity of a surface of the elasticmember and passing through a portion in which a stress generated duringtorsional deformation of the elastic member is small.
 5. The torsionalrocking structural component according to claim 4 wherein the wiringsextend, avoiding the vicinity of a geometric center of the surface ofthe elastic member.
 6. The torsional rocking structural componentaccording to claim 5 wherein the wirings extend, avoiding the vicinityof geometric corners of the surface of the elastic member.
 7. Atorsional rocking structural component comprising: a movable plate; anelastic member for rockably supporting the movable plate, the elasticmember having a rectangular parallelepiped shape, and a rectangularsurface; a support for holding the elastic member; and an even number ofwirings passing through the elastic member, disposed in the vicinity ofa surface of the elastic member and passing through portions in which astress generated during torsional deformation of the elastic member issmall.
 8. The torsional rocking structural component according to claim7 wherein the even number of wirings extend, avoiding the vicinity of ageometric center of the surface of the elastic member, and arrangedsymmetrically with respect to the rocking axis.
 9. The torsional rockingstructural component according to claim 8 wherein the even number ofwirings extend, avoiding the vicinity of geometric corners of thesurface of the elastic member.
 10. A torsional rocking structuralcomponent comprising: a movable plate; a pair of elastic members forrockably supporting the movable plate, each of the elastic membershaving a rectangular parallelepiped shape, and a rectangular surface; asupport for holding the elastic members; and wirings passing through theelastic members, disposed in the vicinity of a surface of the elasticmembers and passing through portions in which a stress generated duringtorsional deformation of the elastic member is small.
 11. The torsionalrocking structural component according to claim 10 wherein the wiringsare located so that one of them is provided in each of the elasticmembers.
 12. The torsional rocking structural component according toclaim 10 wherein the wirings extend, avoiding the vicinity of ageometric center of the surface of the elastic member, and arrangedsymmetrically with respect to the rocking axis.
 13. The torsionalrocking structural component according to claim 12 wherein the wiringsextend, avoiding the vicinity of geometric corners of the surface of theelastic member.
 14. The torsional rocking structural component accordingto claim 10 wherein the wirings are located so that a even of them areprovided in each of the elastic members with the even of wires arrangedsymmetrically with respect to the rocking axis.
 15. The torsionalrocking structural component according to claim 10 wherein the wiringsare located on one of the elastic members, and the torsional rockingstructural component further comprises a strain detection elementdisposed in the vicinity of a surface of the other elastic member andpositioned at a portion in which a stress generated during torsionaldeformation of the elastic member is large.
 16. The torsional rockingstructural component according to claim 15 wherein the strain detectionelement is located at one of the geometric corners of the surface of theelastic member.